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A series of metal β-diketonates were irradiated with bremsstrahlung of maximum energy of 50 MeV and the recoil behavior of7Be, formed from12C of ligands through12C(γ, αn)7Be reaction, was investigated.7Be nuclides thus formed were detected partially as central metal atoms of the complexes. Complex yields of7Be were compared and an anomalously high yield was observed in tris-acetylacetonatocobalt(III) [Co(acac)3].

Shortly before the Second World War time, Nishina reported on a series of prominent nuclear physical and radiochemical studies in collaboration with Kimura. They artificially produced (231)Th, a member of the natural actinium series of nuclides, by bombarding thorium with fast neutrons. This resulted in the discovery of (237)U, a new isotope of uranium, by bombarding uranium with fast neutrons, and confirmed that (237)U disintegrates into element 93 with a mass number of 237. They also identified the isotopes of several middle-weighted elements produced by the symmetric fission of uranium. In this review article, the highlights of their work are briefly summarized along with some explanatory commentaries.

Intertidal coastal and estuarine sediments from 24 sites in the Irish Sea have been analyzed for99Tc,237Np,238Pu,239,240Pu and241Am. The237Np activity and239Pu/240Pu ratio were measured simultaneously by ICP-MS, and99Tc was determined by HR-ICP-MS which is ten times more sensitive than Q-ICP-MS.

A new analytical technique using inductively coupled plasma mass spectrometry (ICP-MS) was applied to the determination of 99Tc in some environmental samples. The accuracy and precision of the new method were assessed by comparison with those of the liquid scintillation counting method. The results obtained by ICP-MS were in good agreement with those by liquid scintillation counting at a relative deviation of 3%. The detection limit is 1.1 mBq/mL (1.73 pg/mL).

This review describes applications of inductively coupled plasma mass spectrometry (ICP-MS) to the determination of long-lived radionuclides in environmental samples. Simultaneous determination of 232Th and 238U in biological samples is described in detail; in this procedure an internal standard, Tl or Bi, is adopted for correction of the matrix effect. Determination of 237Np in soil samples by ICP-MS is also described. It is chemically separated to ensure no interference from matrix elements. The detection limits are several mBq (several pg) for the case of radionuclides having a half life of thirty or forty thousand years.

The adsorption behaviors of niobium and zirconium on silica gel and some other adsorbents were investigated in various concentrations of nitric acid or hydrochloric acid. Niobium is strongly adsorbed on silica gel in a concentrated nitric acid solution, while zirconium is not. In a concentrated hydrochloric acid solution, niobium is weakly adsorbed. Based on the results, a new simple separation method of niobium from other radionuclides especially zirconium is developed. In this method, niobium can be recovered by 81%, and separation from zirconium is complete.The method was applied to separation of radioniobium from the neutron-irradiated zirconium wire and from the neutron-irradiated uranium with the results of complete elimination of other radionuclides present.

The concentration of129I in soil in Japan was determined by neutron activation analysis. For the activation analysis, pre-irradiation chemical separation of the iodine was carried out by acid decomposition and distillation and post-irradiation treatment was performed by ion exchange and solvent extraction. The concentration of stable iodine and137Cs were also determined and compared with the behavior of129I in soil.

Plutonium and uranium in human tissues obtained from residents of the Tokyo area were determined by a-spectrometry and the fission track method, respectively. The distribution pattern of each element was estimated on the basis of mean concentration obtained. Plutonium is concentrated in some special organs, while uranium is distributed rather generally throughout the whole body. This difference of distribution tendency is considered to be due to the characteristics of stable chemical states of the elements in body fluid; Pu4+ for plutonium and UO2(2+) for uranium.

環境試料中の60Coの簡易迅速分析法を考案した。この方法は60Coの水酸化物沈殿への共沈, 陰イオン交換およびTOA抽出による分離, そして液体シンチレーションカウンターによる測定とから成っている。操作全体を通じての担体回収率は95%以上, 計数効率は80%であった。この方法により, 海水および海藻灰の分析を行った。

The isotopic exchange method is studied for the simultaneous determination of radioactive and stable isotopes of cobalt in environmental samples. Radioactive cobalt is isotopically exchanged with Co-CyDTA in HC1 solution of the sample. The solvent extraction method is used for the separation of Co2+ and Co-CyDTA species from each other. The amounts of radioactive and stable cobalt isotopes are calculated with activities of Co and Co-CyDTA at the exchange equilibrium. The methods for eliminating interfering ions are discussed. The results are in good concordance with those obtained by the conventional analytical methods.

The distribution of radioiodine (131I) species in rain water collected at Tsukuba in May 1986 was studied using the isotopic exchange method. Organic-soluble forms of radioiodine were not observed. Iodide (I∗−) was the predominant species, and the concentration of iodate (I∗O3−) was less than half of I∗−. The results were compared with those for 131I produced by neutron-irradiation of uranyl nitrate.

核異性体を (γ, γ′) 反応によって作る原子核過程は古くから知られているが, これを放射化分析, γ線量測定あるいはホットアトム化学などに応用する研究は特色ある方法であるにもかかわらず従来あまり広く用いられていなかった。しかし最近に至るまでの研究の積み重ねによって, 重要な応用分野が開けつつあり, これに対する国際的な評価が高まってきた。本稿は1977年10月日本学術振興会の招きにより来日したハンガリー同位体研究所長Veres博士と池田, 吉原らの共同討議による研究成果のまとめである。(γ, γ′) 反応は畜産上重要なセレンの放射化分析に利用され, あるいは考古学的な貨幣中の銀含量の決定に利用されている。迅速な非破壊分析が可能であり, かつ中性子放射化分析のように残留放射能を生じないなどの優れた点をもっている。また高線量のγ線源に対してこの反応を用いると, γ線量測定ができ, ひいてはそのγ線源のキュリー数の決定ができる。さらに原子炉の使用済み燃料の燃焼度 (burnout) を評価するさいに, この反応を適用することが可能である。固体ホットアトム化学でホットアトム効果ρ出現するしきいエネルギー (出現エネルギー) はこの方法ではじめて実測された。115In (γ, γ′) 115mIn反応をインジウムedta錯体中で起こし, 錯体からはずれる115mIn3+を化学的手法で観察する。ホットアトム化学での重要な成果である。

Uranium in Japanese tobacco leaves and in Japanese human hair was determined by the fission track method. It was found that the uranium content in smokers' hair was higher than that in non-smokers' one and a part of uranium was lost from tobacco leaves by ashing at 500–700 °C. These two results suggest that uranium would be inhaled through smoking.

有機ヨウ素化合物中のヨウ素の定量に, 著者らは新しい同位体交換分析法を開発し, いくつかの有機化合物について定量を行った。そのさい適当な同位体交換反応速度をもつ系を見出す目安として, 活性化エネルギーを求め, 有機ヨウ素化合物の構造, 試薬濃度, 溶媒等との関係を検討した。均一系では活性化エネルギーはCH3I

Porcelain teeth, some of which contained uranium compounds for aesthetic purpose, have been widely used in dental clinics. Recently, the hazardous effects by uranium radiation were suggested.In the present study, the authors carried out the determination of uranium concentrations of four major brands of porcelain teeth marketed in Japan using the fission track method, and the absorbed doses of oral tissues were calculated by the authors' introduced formula for calculation of alpha radiation.Average uranium concentrations of the brands studied were determined 3.6ppm (0.33-10ppm, Japan), 18ppm (0.69-81ppm, Japan), 9.4ppm (2.5-14ppm, Japan) and 82ppm (11-205ppm, U. S. A.), respectively. The corresponding dose equivalents at the surface of oral mucosal membrane were 2.9rem y-1, 14rem y-1, 7.6 rem y-1 and 66rem y-1.

Some water-soluble organic iodine compounds (aqueous solution) can be analyzed for iodine by isotopically exchanging with labelled elementary iodine (organic solution). The method is applicable to exchange systems in which the rate of the exchange is rather small but measurable, before the exchange equilibrium is attained. The iodine content of iodoaromatic amino acids such as 5-iodouracil and 3,5-diiodotyrosine can be determined within an error of ±4%.

The adsorption behaviour of trace amounts of tellurate, tellurite, iodide and iodate on active charcoal has been studied by a radioactive-tracer method; on the basis of the results, a column chromatographic separation of these ions from each other was devised. By passing the sample solution (at pH 5.6) through an active charcoal column, all but tellurate are retained, lodate, tellurite and iodide are then eluted successively with water (pH 7.0), 0.1 N hydrochloric acid and 1 N sodium hydroxide, respectively. The method can be applied to the preparation of radioiodine from a neutron-irradiated tellurate target.

テノイルトリフルオロアセトン〔TTA〕 (クロロホルム溶液) ―0.1M過塩素酸塩 (水溶液) 系におけるイットリウムの溶媒抽出挙動を, 88Yをトレーサーとして, 25℃で調べた。有機相のTTA濃度10-2～10-1M, 水相のpH3～6の範囲における分配係数の変化は, YA3の有機相への抽出と, 水相におけるYA2+, YA2+およびYA3の生成として説明される (AはTTAのアニオン部を示す) 。Y3++3HA (org) 〓YA3 (org) +3H+の反応の平衡定数として, K0=2.82×10-9の値が得られた。

The activation of indium by gamma-ray source through absorption of photons of resonance energy and the threshold energy (appearance energy) determination in indium compounds as well as some results of hot atom chemistry studies of indium compounds and of implantation with indium ions are described.

Fission track /FT/ method and inductively coupled plasma mass spectrometry /ICP-MS/, that is a new analytical technique for the analysis of trace element, were used for the measurement of240Pu/239Pu ratios in environmental samples. The results obtained by both methods are in agreement within the relative deviation of 9–13%. The precision in ICP-MS was found to be better than in it the FT-method. These methods are applicable to measure the Pu isotopes ratio at low concentration levels in environmental samples.

The retentions of cobalt, copper and zinc recoils were studied in the mixed crystal system of α-cobalt phthalocyanine and α-zinc phthalocyanine. It was suggested that a part of the retentions of cobalt and zinc recoils was due to a competitive process. The relationship between the retentions of the zinc recoils and their recoil energy in different matrices was discussed.

The radioactivity released by the reactor accident at Chernobyl was detected in surface air at Tsukuba, Japan. Gamma-spectrometry of airborne dust collected using aerodynamic separation showed higher concentrations of radionuclides in fine particles. The particle-size distribution of radionuclides changed with time.

Uranium and calcium contents in human bones (skull, rib and femur) were determined by the fission track method and the inductively coupled plasma-atomic emission spectroscopic method (ICP-AES), respectively. The U/Ca concentration ratio in the bones was found to decrease in the order of rib greater than femur greater than skull, which is in accordance with the decreasing order of the mean annual replacement percentage of bone components. Several femur bones were cut into several longitudinal segments, and uranium and calcium contents in each segment were determined. Among these, the U/Ca ratio in the epiphysis was higher than those in the diaphysis.

The formation of99mTc was observed when99Tc was irradiated by reactor neutrons as a result of the99Tc(n, n)99mTc reaction. A good linearity was observed between the activities of99mTc produced and99Tc irradiated. The cross section of the excitation reaction was estimated to be 0.24 b. The application of the nuclear excitation reaction to the activation analysis for low level99Tc was studied.

Monthly variations of tritium, deuterium and SO42- concentrations in waters from a fumarole, seven hot springs, three rivers, and precipitation in the Nasu volcanic area were measured to investigate their origin and subsurface behavior. Most of waters in the Nasu district including fumarolic condensate are considered to be of meteoric origin on the basis of their δD values. Hot-spring waters are classified into three groups according to their tritium concentration, i.e., the Group A waters with T=30 ∼ 70TR (as of 1974), Group B waters having T=50 ∼ 100TR with seasonal variation, and Group C waters with T=3 ∼ 30TR and high δD values. A model is proposed that the water reservoirs are divided into three stratified aquifers, i.e., layers I, II and III, each of which is characterized by respective tritium concentration. The tritium concentration of the shallowest layer-I water is close to the annual average tritium concentration for precipitation at the time of sampling (1974). The age of the layer-I water is considered to be less than a few years. The layer-II water occurs deeper than the layer-I, and is 5 ∼ 12 years old. The layer-III water occurs beneath Nasu volcano, is very old and contains no tritium. Mixing of waters from the different layers produces Group A, B and C waters. Change in the mixing ratio causes seasonal variation in the isotopic and chemical compositions of some hot-spring waters.

A new analytical technique using ICP-MS was applied to the determination of237Np in some environmental samples. The accuracy and precision of the new method were assessed by comparison with those of conventional NAA and α-spectrometric method as well as by analysis of the intercomparison sample of Ravenglass NRPB silt. The results obtained by ICP-MS were in good agreement with those by NAA or α-spectrometry at a relative deviation of 2–9%. The detection limit is 0.02 mBq/ml (26 mBq=1 ng).

Determination of 15 elements in the dental porcelain powders (Vita VMK 68) marketed in Japan was done by means of non-destructive neutron activation analysis. The potassium and sodium contents showed less variations from powder to powder, and the uranium contents varied from a few ppm to 1090 ppm in a wide range. The high contents of uranium (345--1090 ppm) were detected in the powders of Enamel, Dentin, Effect, Color and Gum which were used for the superficial parts of a porcelain crown, while the low contents of uranium (1.6--2.7 ppm) were detected in those of Opaque and Translucent which were used for the core part and the top of the crown. Cerium and samarium were also detected in each powder in the amounts similar to those of uranium. The main radionuclides present in the porcelain powders were 238U, 235U, 234U, 234mPa, 234Th, 231Th and 40K. The activities of these nuclides were calculated and discussed.

Several human lung samples were dissected into lobes and uranium and silicon contents in each lobe were determined by the fission track method and the inductively coupled plasma-atomic emission spectrometry (ICP-AES), respectively. It was found that both uranium and silicon concentrations were high in the upper lobe compared with those in the lower one. Though the tendency may be mainly interpreted by the deposition way of airborne dust in the lung, the higher U/Si concentration ratio in the upper part than that in the lower part of lungs may suggest the partial removal of uranium deposited in the lower part of the tissue.

Tritium, deuterium and chloride concentrations in the Arima hot spring waters were measured as a clue to their origin and subsurface behavior. T-D-Cl- relationships clearly indicate that the saline brine of deep origin (T = 0 TR, δD = -30‰ and Cl- = 43 g/l) is mixed with young meteoric water having T = 30 TR, δD = -50 ‰ and Cl- = 0g/l in varying proportions to form a group of high chloride hot spring waters. The young meteoric water in a shallow aquifer is also mixed with the older meteoric water in a deeper aquifer characterized by high tritium concentration (∼100TR), forming another group of low chloride waters. The mixing ratio of the two meteoric waters varies with season.

The uranium content of several human tooth, bone and soft tissue samples was determined by the fission tract method. The average uranium content in teeth, bones and soft tissues were 6.7, 8.4 and 64 ppb ash, respectively. The distribution of uranium in bones is less uniform than that of teeth, and the uranium content of soft tissues is generally higher than that of teeth and bone. The presence of thorium does not interfere with the uranium determination in most cases.

3価のユーロピウムの溶媒抽出挙動をテノイルトリフルオロアセトン (TTA; HA) のクロロホルム溶液―0.1M過塩素酸塩系でしらべた。有機相中のTTA濃度を10-4～10-1Mに変え, また水相中の水素イオン濃度を10-3～10-7Mに変えたときの分配係数の変化は, EuA3の有機相への抽出と水相中でのEuA2+, EuA+2およびEuA3の生成として説明される。つぎの諸反応の平衡定数は以下のようである。Eu3++3HA (有機相) 〓EuA3 (有機相) +3H+K0=2.95×10-9Eu3++A-〓=EuA2+ β1=4.5×104Eu3++2A-〓EuA+2 β2=4.7×109Eu3++3A-〓EuA3 β3=1.1×10122価のユーロピウムのTTA抽出の分配係数は対応する3価のユーロピウムに比べて一般に小さく, pH 4.2～4.8で両者の相互分離が可能であることが示された。

The application of the color reaction between basic lanthanum acetate and iodine to the quantitative analysis has long been the problem left to be solved. Recently, hawever, Hutchens and Kass succeeded in application of this color reaction to the micro-determination of acetate ions with good results. The present authors examined this method and confirmed that satisfactory results were obtained in its application. In addition, the authors found that the corresponding reactions for praseodymium and neodymium were applicable, too, to the same purpose, although in these cases the sensitivity was not so good as that in the case of lanthanum.

In order to find the proper method of medical treatment for the afflicted men on board the No.5 Fukuryu Maru on March 1, 1954, it was necessary to know the species and amounts of radioactive elements in the dust of the so-called Bikini Ashes which had fallen on board.At the request of the Hospital of Tokyo University, the authors started analyses on March 18.A combined method of chemical separation with the use of carriers and separation with the use of ion exchange resin was applied;17 nuclides were detected and the results of quantitative estimation of alkaline earth metals were reported on March 31.The main constituent of the ashes was found to be calcium hydroxide and its radioactivity was 0.37mC/g (April 23) which was decayed proportionally to -1.37 power of the time elapsed.The chemical group separation was carried out as shown in Table 3; the second, third(especially rare earth metals)and fifth(alkaline earth metals)analytical groups showed strong radioactivity.By ion exchange method(Fig. 4), the fraction of anions, Zr and Nb fraction, U fraction, the fraction of rare earth metals and the fraction of alkaline earth metals were separated.Furthermore, each constituent of those fractions was estimated quantitatively.In order to confirm the presence of 129mTe, 129Te, 131I, 132I, 103Rn, 106Ru, 106Rh, 95Zr and 95Nb, the chemical method was used.The members of alkaline earth metals, e.g.45Ca, 89Sr, 90Sr, (90Y), 140Ba and (140La), and the members of rare earth metals, e.g.91Y, 141Ce, 143Pr, 144Ce, 144Pr and 147Nd were estimated after the separation with the use of ion exchange resin.The presence of 237U was confirmed from its radioactivity and chemical properties.Also α-tracks of 239Pu.were detected by autoradiograph ic method.Table 6 indicates the summary of the results.

放射性バリウム140Baからその娘核種の放射性ランタン140Laを無担体で分離することは,共沈法などによりすでに行われている.この研究では同様の分離をより容易に,かつ迅速に行う目的で塩酸による溶出法を試みた.140Baの溶液に非放射性の塩化バリウムを担体として加え,均一沈殿法により硫酸バリウムとして沈殿させ,ロ紙上に移して放置し,140Laを生成させる.この沈殿に種々の濃度の塩酸を溶出剤としてそそぎ,流出液について140Laと140Baの検出を行い,分離が完全に行われているかどうかをしらべた.その結果3N塩酸-エチルアルコール(1:1)を溶出剤として用いるのがもっともよいことがわかった.

Summary The apparent similarity of the rare gas diffusion and the recoil annealing processes both resulting in “pseudo-plateaux” leads to study these processes in CaCrO4-crystals in order to find out a possible relationship. The material used was crystallized from solution, dried at room temperature (sample A) and at 200° C (sample B), an average grain size of 130 μ was selected and irradiated for 8 hours with pile neutrons in a flux of 4 x 1012n/cm2 · sec. The diffusion of the homogenously distributed 37Ar, produced by 40Ca (n, ɑ) process was investigated in the temperature range from 100 to 800° C. The thermal annealing of (n, γ) 51Cr-recoil fragments could be measured between 100 and 300° C. - It was found that the percentage of released 37Ar is much dependent on the thermal treatment of the CaCrO4-crystals. For instance about 52% of the 37Ar diffused already in 3 hours at 300° C from sample (A), while from the tempered sample (B) only about 5% was lost. In both preparations the 37Ar-release reaches 100% at about 800° C possibly favoured by oxygen liberation. In the range of 300 ~ 700° C, linearity of log D with 1/T was observed. This part of the curve should be due to the normal volume diffusion. 37Ar-diffusion coefficients at 200° C were measured to be 6,0 · 10-11 cm2/sec for sample (A) resp. 7,7 · 10-15 cm2/sec for sample (B). At 300° C, 3,2 · 10-10 for (A) resp. 1,1 · 10-12cm2/sec for (B). The initial retention of recoil 51Cr was found to be 10% higher in sample Β which can be explained by the fact that the instantaneous recombination reaction is hindered by adsorbed molecules and lattice imperfection. The thermal annealing at the earlier stage formally follows first order kinetics, the reaction rate constants are almost the same for both samples at a given temperature. In multi-step annealing experiments R∞ reaches characteristic plateau-values which can be obtained also by a single-step heating at the respective temperature. This is not the case in the multi-step 37Ar-diffusion experiments which are found to be very sensitive to the "history" of the sample. The differences in the Ar-diffusion and the 51Cr-annealing-multi-step curves are explained by the pronounced physical and the more chemical nature of the processes involved.

電解により90Sr-90Y中性溶液から高純度の無担体90Yを単離する迅速法を報告した.放射化学的純度は99.9%以上であり収量を問わないならば無担体90Yを数分間で調製することができる.90Sr-90Y溶液をpH5～6に調節し,白金を両極(陰極には銅を代用してもよい)として2～6ボルトの電圧をかけると無担体90Yが陰極にだけ析出する.陰極上とのイットリウムは使用目的に応じて酸で溶出することができる.電解液の支持塩は硝酸アンモニウム,硫酸アンモニウム,塩化アンモニウムのいずれでもよい.ストロンチウムの担体を含むときには硫酸塩を使えないことはいうまでもない.

140Ba-140La系から放射化学的純度の高い無担体140Laを電解により迅速に調製する方法を確立することを目的として種々の条件を検討した.銅円板陰極を用いる場合,電解液の無関係塩として硝酸塩を用いると電解中にpHの変化をきたし,純度および収率が悪くなる.これに反して,硫酸塩または過塩素酸塩を用いるときはpHに変化が見られず,純度・収率ともに良好である.硫酸塩を用いるときは,その濃度が低くなるにつれて純度が低下した.結局,0.1M NH4ClO4-0.01M Ca(ClO4) 2-140Ba-140La過塩素酸塩系電解液から,白金を両極として,6ボルトで所定の時間電解を行えば,純度99.9%以上の140Laをかなり良好な収率で調製できる.同様の電解液を90Sr-90Y系からの90Yの分離に適用し満足すべき結果を得た.